When a vehicle body is conveyed through welding and assembling steps, etc. on an automotive vehicle assembly line, the conveying efficiency is rather lowered due to the differences in the details of work in the individual steps even when an attempt is made so as to maintain a constant vehicle conveying speed. That is, it is more efficient to convey the vehicle body at a low speed during each of the welding and assembling steps, and, after this welding and assembling step, to convey the vehicle body at a high speed between that step and the next welding and assembling step.
Therefore, in the finishing steps which are performed after the welding and assembling steps on the vehicle body are completed to a certain extent, and in which the operator makes necessary finishing including external appearance check, finish working, repair, etc., it is a common practice that the vehicle body having been subjected to a certain extent to the required welding and assembling is conveyed by a shuttle conveyor onto a roller conveyor, and the vehicle body is then conveyed by this roller conveyor onto a slat conveyor disposed at the finishing station to permit the required finishing by the operator.
In this case, the shuttle conveyor conveys the vehicle body onto the roller conveyor while supporting left and right side members fixed by welding to a floor panel of the vehicle body. Therefore, the roller conveyor conveys the vehicle body toward the slat conveyor while supporting left and right side sills of the vehicle body.
The roller conveyor is composed of many rollers of the shape of round bars having the same diameter and arranged in parallel to each other, and a force for rotating these rollers in one direction is imparted to the rollers so as to convey the vehicle body placed on the rollers. At the delivery end of this roller conveyor, its end roller is located in close proximity to the receiving end of the slat conveyor so that the vehicle body can be smoothly transferred from the roller conveyor to the slat conveyor.
However, when the vehicle body is conveyed onto the slat conveyor while being supported at the left and right side sills by the roller conveyor and these side sills ride over the individual rollers, such a problem may arise that the vehicle body cannot be smoothly conveyed due to engagement of the ends of the side sills with the rollers, and the side sills tend to be hurt by engagement with the rollers.
On the other hand, when a belt conveyor is used in lieu of the roller conveyor, such another problem may arise that a large gap is formed between the delivery end of the belt conveyor and the receiving end of the slat conveyor by the presence of a drive mechanism disposed between the delivery end of the belt conveyor and the receiving end of the slat conveyor, with the result that the vehicle body cannot be smoothly transferred.
Further, the shuttle conveyor has engaging pins engageable with engaging holes formed on the side members of the vehicle body, and, when the shuttle conveyor is advanced to receive the vehicle body on the belt conveyor until the vehicle body is completely transferred onto the belt conveyor. The shuttle conveyor is then retracted, so that one vehicle body after another can be successively placed on the belt conveyor.
However, because the shuttle conveyor supports the vehicle body by the engaging pins engaging the corresponding engaging holes formed on the side members of the vehicle body, the vehicle body cannot be disengaged from the shuttle conveyor, and the shuttle conveyor cannot be retracted, unless the engaging pins of the shuttle conveyor are disengaged from the corresponding engaging holes of the vehicle body after the vehicle body is transferred onto the belt conveyor. In order to disengage the engaging pins from the engaging holes, it is necessary to move downward the engaging pins or the whole supporting mechanism. However, this requirement provides the problem that the structure becomes inevitably complex.